In recent years, servers that provide games to portable devices via a communication network have become widespread. An example of games provided by such servers includes a game played by using game content groups each formed by multiple game contents that are digital contents such as cards.
For example, Japanese Laid-open Patent Publication No. 2013-034828 discloses a game in which users use decks each corresponding to a card group formed by one or more cards registered in a game system in advance and each of the users takes cards from their decks to lay the cards down.
In the game system disclosed in Japanese Laid-open Patent Publication No. 2013-034828, a user device displays a display screen for creating and editing a deck, the display screen including a deck formation area and an owned-card area. A user can create a deck by selecting a card to add to the deck from the owned-card area, and then dragging and dropping the icon corresponding to the card to the deck formation area.